Surgical fixation system and related methods

ABSTRACT

A surgical fixation system including a base plate, a plurality of anchors and a locking element. The base plate has at least a pair of fixation apertures configured to receive at least a portion of the anchors therethrough. The fixation apertures are located within the base plate such that upon proper placement of the base plate within a surgical target site, one of the fixation apertures is positioned over a first bone segment (e.g., a first vertebral body), and the other fixation aperture is positioned over a second bone segment (e.g., a second vertebral body).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/666,933, filed Nov. 1, 2012, which is a nonprovisional patentapplication claiming the benefit of priority under 35 U.S.C. § 119(e)from U.S. Provisional Patent Application Ser. No. 61/554,430, filed onNov. 1, 2011, the entire contents of which is hereby expresslyincorporated by reference into this disclosure as if set forth fullyherein.

FIELD OF THE INVENTION

The present invention relates generally to spinal surgery, and moreparticularly, to systems and methods for repairing and/or reconstructingskeletal structures.

DISCUSSION OF THE PRIOR ART

Each year millions of people suffer from back pain arising from defectsin the intervertebral space. Commonly, surgical interventions directedat promoting fusion across the affected joint are employed topermanently provide long term pain relief to the patient. Typically,such fusion surgeries involve performing a partial or completediscectomy to prepare the disc space, and then implanting a natural orsynthetic intervertebral fusion implant within the prepared disc space.Supplemental fixation, such as bone plates (implanted on the anterior orposterior aspect of the spine) or rod systems (implanted on theposterior aspect of the spine) may be further employed to providestability across the affected joint while the body goes through thefusion process. Plate implants have been used for many years to aid inthe promotion of fusion across affected vertebral disc spaces throughstabilization of the joint. These spinal fixation plates are directed atcomplete immobilization of the affected joint while affording theoptional benefit of restricting fusion inducing materials (such as bonegrafts) within the joint. As a result of the fusion of adjacentvertebral bodies, the disc height between the vertebral bodies isrestored, thereby reducing pain in the patient.

During a lateral access surgery performed through a minimally-invasiveoperative corridor, it can be a challenge to obtain the angle orexposure necessary to properly implant an anterior or posteriorsupplemental fixation apparatus. Often, additional incisions must bemade to accommodate placement of such devices. Lateral fixation plateshave been developed to address some of these difficulties, however theseplates are not without their challenges. Base plates of shorter lengthsfacilitate the ease of insertion into and through the minimally-invasivesurgical corridor, but plates of longer lengths may be required forsuccessful performance of the procedure. Benefits of minimally invasivelateral approaches to the spine include decreased morbidity, decreasedoperative times, reduced blood loss, shortened hospital stays, andimproved cosmesis. However, these benefits of minimally invasiveprocedures may not be effectuated where the length of the plate requiredto fix vertebral bodies does not allow for adequate insertion of theplate through the surgical corridor.

The present invention is directed at overcoming, or at least reducingthe effects of, one or more of the problems set forth above.

SUMMARY OF THE INVENTION

The present application addresses these problems by providing a surgicalfixation system including a base plate, a plurality of anchors, and atranslating locking element that is expandable in situ. The examplesshown and described herein are in the form of a base plate configuredfor a single-level spinal fusion, and as such the bone plate is sizedand configured to span a single intervertebral space while achievingpurchase within each of the vertebral bodies adjacent the singleintervertebral space. However, the base plate may be provided in anynumber of sizes to accommodate multiple-level spinal fusions withoutdeparting from the scope of the present invention, depending upon theneeds of the specific user. The base plate may also be provided in anynumber of shapes suitable for spanning at least one intervertebral discspace without departing from the scope of the invention. The base plateis particularly suitable for lateral insertion and placement against alateral aspect of the vertebral bodies, however other uses are possiblewithout departing from the scope of the present invention.

The base plate is provided with a pair of first fixation aperturesconfigured to receive at least a portion of first bone anchorstherethrough. The first fixation apertures are provided by example aslarge circular holes, however the first fixation apertures may beprovided with any shape suitable for receiving at least a portion of thefirst bone anchors therethrough, including but not limited to ovoid orpolygonal without departing from the scope of the present invention. Thefirst fixation apertures are comprised of a first pocket and a secondpocket and are sized and dimensioned to receive the first bone anchors.The base plate is further provided with a pair of second fixationapertures configured to receive at least a portion of second boneanchors therethrough. The second fixation apertures as generallycircular holes, however the second fixation apertures may be providedwith any shape suitable for receiving at least a portion of the secondbone anchors therethrough, including but not limited to ovoid orpolygonal without departing from the scope of the present invention. Thesecond fixation apertures have a first pocket and a second pocket andare sized and dimensioned to receive the second bone anchors. The firstand second fixation apertures are located within the base plate suchthat upon proper placement of the base plate within a surgical targetsite, one of the first and second fixation apertures are positioned overa first bone segment (e.g. a first vertebral body), and the other firstand second fixation apertures are positioned over a second bone segment(e.g., a second vertebral body).

The base plate is further provided with two components: a femalecomponent and a male component. The female component comprises one firstfixation aperture, one second fixation aperture, a receiving slot, and alengthening slot. The male component comprises one first fixationaperture, one second fixation aperture, an insertion portion, and alocking aperture. The insertion portion of the male component is sizedand dimensioned to snugly fit within the receiving slot of the femalecomponent. The male and female components of the base plate aresecuredly mated to one another via the translating locking element.

In its assembled state, the base plate has a first end, a second end, afirst side, and a second side. The base plate further includes a firstsurface and an opposing second surface. When properly positioned on alateral aspect of a spinal column, the second surface interfaces withthe bone and thus is a vertebral contacting surface. Moreover, the firstend represents the cephalad-most (or top) end of the base plate, thefirst side represents the posterior-most (or back) side of the baseplate and the second side represents the anterior-most (or front) sideof the base plate. First and second ends preferably each have a radiusof curvature that is approximately equal to the radius of curvature ofthe retractor blades of a surgical retraction system.

The second surface of the base plate may include one or more protrusionswhich engage the bones of the vertebral bodies, the disc space, or thevertebral spacer. This engagement prevents the base plate from movingwhile the plurality of bone anchors is being placed. Base plate may alsohave one or more engagement features for engagement with an insertiondevice, for example a translating plate inserter.

The first bone anchors may be, by way of example only, threaded bonescrews, however other forms of anchors are possible without departingfrom the scope of the present invention. The bone screw comprises ascrew head and a shank. The shank includes threads for threaded purchaseinto a bony segment (e.g. vertebral body). The screw head is comprisedof an upper screw head region, a plurality of locks, a lock screw, and abottom spherical portion.

The surgical fixation system also includes a locking mechanism forfixedly coupling the first and second bone anchors to the base plateafter implantation. According to one embodiment, the fixation apertureseach have a first spherical pocket and a second spherical pocket sizedand dimensioned for receiving a bone screw therein. The bone screw isplaced through the base plate and mates with the first spherical pocketwithin the base plate via the matching a bottom spherical surface of thebone screw. The bone screw has a cone of angulations in which it can beplaced and still lock to the plate. Locks have a spherical inner facewhich fit into the second spherical pocket. Once the bone screw is fullyseated within the first spherical pocket, a driver mechanism may rotatethe lock screw via the inner tool engaging recess towards the interiorof the of the screw head. With the locks fully engaged, furtherpolyaxial motion of the bone screw is prevented as is unwanted backoutof the bone screw.

The second bone anchors may be provided, by way of example only, in theform of bone staples, however other forms of anchors are possiblewithout departing from the scope of the present invention. The bonestaple comprises a staple head and an elongate body. The elongate bodypreferably includes a pointed distal tip for purchase into a bonysegment (e.g., vertebral body). The bone staple has blades that run downthe length of the elongate body. The flat faces of the blades (forexample, in a cruciform configuration) prevent rotation of the bonestaple about its central axis. Because the bone staple is not threaded,it can be impacted into the bone quickly, thereby reducing the timerequired for implantation. The staple head is mated and locked to thebase plate via first and second spherical pockets the same way asdescribed above for the bone screw.

In minimally invasive lateral approaches to the spine, base plates ofshorter lengths facilitate the ease of insertion into and through thesurgical corridor. However, depending on patient's anatomy and/orsurgical requirements, base plates of longer lengths may be advantageousnotwithstanding the difficulties associated with inserting a longerplate. In a preferred embodiment of the present invention, the baseplate of the surgical fixation system contains an in situ lengtheningfeature (translating locking element) that allows the length of the baseplate to be variably lengthened in situ. In the closed position, themale portion of the base plate is fully inserted into the female portionsuch that the set screw is maximally situated within the lengtheningslot. In the open position, the male insertion portion is extended awayfrom the female receiving slot such that at least some portion of themale insertion portion is not contained within the female receivingslot. This distance of such a non-contained portion is limited by thedistance between the two ends of the lengthening slot within thetranslating locking element.

In a preferred embodiment, the base plate is inserted in its smallest,closed configuration via a lateral approach to lateral aspect of thespine. Once the base plate has reached the spinal target site, the platemay be lengthened until the set screw prevents any further extensionwithin the lengthening slot. Once the desired length has been achieved,the translating locking element may be secured, thereby locking thelength into position.

The base plate, anchors and/or locking components etc. may be formed ofany material suitable to provide rigid fixation between two bonysegments. By way of example, all may be formed of a biocompatible metal,such as titanium. The base plate may be provided with any size necessaryto complete the desired spinal fixation.

The surgical fixation systems of the present invention are assembled insitu during a surgical procedure. One such example is a spinal fusionsurgery. The surgical fixation systems disclosed herein are optimallyused in a direct lateral surgical procedure in which the spine isapproached laterally at approximately a 90° angle relative to thepatient's spine. The first step in such a procedure is to create anoperative corridor through the patient's skin and underlying musculatureto the spinal target site, for example, a symptomatic intervertebraldisc located between first and second adjacent vertebral bodies. Thespecific technique involved in performing this step is shown anddescribed in commonly-owned U.S. Pat. No. 7,905,840, filed on Oct. 18,2004, patented on Mar. 15, 2011, and entitled “Surgical Access Systemand Related Methods,” the entire contents of which are herebyincorporated by reference into this disclosure as if set forth fullyherein.

After establishment of the operative corridor to the surgical targetsite, the next step is to perform the necessary therapeutic technique torelieve the distress on the target disc space. For example, this mayinvolve performing a partial or total discectomy (removing damaged ordegenerative disc tissue from the intervertebral space) and theninserting a spinal fusion implant such as a bone graft (e.g., allograft,autograft, or xenograft) or synthetic fusion cage (e.g., titanium and/orPEEK) into the space. One example of a synthetic spinal fusion implantthat may be used is shown and described in commonly-owned U.S. Pat. No.7,819,891 filed on Mar. 29, 2005, issued on Apr. 5, 2011, and entitled“Systems and Methods for Spinal Fusion,” the entire contents of whichare hereby incorporated by reference into this disclosure as if setforth fully herein. These spinal fusion implants (natural or synthetic)may be used with or without additional fusion-inducing materials, suchas an orthopedic matrix containing, for example, calcium hydroxyapatite,bone morphogenic protein (BMP), demineralized bone matrix, collagen bonegraft matrix, and stem cell material, or other fusion-promotingsubstances placed within the spaces of the implant, while the implant isadvanced into the intervertebral space.

After addressing the disc space, the surgical fixation system may beimplanted. A variety of instruments may be provided to assist in theimplantation of the surgical fixation system of the present invention.In accordance with the present invention, there is also provided a plateinserter for inserting the surgical fixation system, preferably from alateral approach. The plate inserter facilitates proper insertion of thebase plate as well as lengthening of the base plate in situ. Once thebase plate is properly seated within the surgical target site, thesurgeon proceeds with pilot hole formation to prepare the vertebralbodies for receiving the first bone anchors. Formation of the pilot holemay be accomplished via a number of different techniques and instrumentsdepending upon the surgeon's preference, including but not limited tousing drills, taps, awls, etc. to create a pilot hole that is preferablyundersized by 1 mm relative to the first bone anchors to be used inorder to maximize the purchase of the bone screws within the bone. Uponformation of the pilot hole, the bone screws and bone staples areinserted into the bone. Insertion of the bone screws may be accomplishedvia a number of different techniques and instruments depending on thesurgeon's preference. Preferably, a driver is used to insert the bonescrews and bone staples into the bone. Once the bone screws and boneanchors are implanted through the base plate and into the vertebralbodies, the locking elements on the bone screws, bone anchors, and platemay be applied to secure the base plate in place and complete theassembly of the surgical fixation system.

At this stage, the surgical fixation system is fully assembled in situand implanted into a surgical target site. The procedure beingcompleted, the operative corridor is closed and the incision is stitchedup.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example of a surgical fixation systemaccording to one embodiment of the present invention;

FIG. 2 is an exploded perspective view of the surgical fixation systemof FIG. 1;

FIG. 3 is a front view of the base plate of the surgical fixation systemof FIG. 1 in a closed configuration;

FIG. 4 is a perspective view of one component of the base plate of FIG.3;

FIG. 5 is a front view of another component of the base plate of FIG. 3;

FIG. 6 is a front view of the base plate of FIG. 3 in an openconfiguration;

FIG. 7 is a back view of the base plate of the surgical fixation systemof FIG. 1;

FIG. 8 is a side view of the base plate of the surgical fixation systemof FIG. 1;

FIG. 9 is a perspective view of a first bone anchor of the surgicalfixation system of Fig.

FIG. 10 is an exploded perspective view of the first bone anchor of FIG.9;

FIG. 11 is a partial perspective view of the screw head of the firstbone anchor of FIG. 9;

FIG. 12 is a perspective view of the lock of the first bone anchor ofFIG. 9;

FIG. 13 is a perspective view of the lock screw of the first bone anchorof FIG. 9;

FIG. 14 is a partial perspective view of the first bone anchor of FIG.9;

FIG. 15 is a perspective view showing the interaction between the locksand the lock screw of the first bone anchor of FIG. 9;

FIG. 16 is a partial perspective view showing the interaction betweenthe locks and the screw head of the first bone anchor of FIG. 9;

FIG. 17 is a perspective view of a second bone anchor of the surgicalfixation system of FIG. 1;

FIG. 18 is a cross-sectional view of the base plate of the surgicalfixation system of FIG. 1;

FIG. 19 is an example of a surgical fixation system according to asecond embodiment of the present invention;

FIG. 20 is a perspective view of one example of a second bone anchor ofthe surgical fixation system of FIG. 19;

FIG. 21 is an example of a surgical fixation system according to a thirdembodiment of the present invention;

FIG. 22 is an example of a surgical fixation system according to afourth embodiment of the present invention;

FIG. 23 is an example of a surgical fixation system according to a fifthembodiment of the present invention;

FIG. 24 is an exploded view of the surgical fixation system of FIG. 23;

FIG. 25 is a perspective view of a first bone anchor of the surgicalfixation system of FIG. 23;

FIG. 26 is front view of the first bone anchor of FIG. 25;

FIG. 27 is an exploded view of the first bone anchor of FIG. 25

FIG. 28 is a cross-sectional view of the first bone anchor of FIG. 25;

FIG. 29 is a cross-sectional view of the first bone anchor situated inthe base plate of the surgical fixation system of FIG. 23;

FIG. 30 is a perspective view of a second bone anchor of the surgicalfixation system of FIG. 23;

FIG. 31 is a front view of the second bone anchor of FIG. 30;

FIG. 32 is a top view of the second bone anchor of FIG. 30 in a firstconfiguration;

FIG. 33 is a cross-sectional view of the second bone anchor of FIG. 30in the first configuration;

FIG. 34 is a top view of the second bone anchor of FIG. 30 in a secondconfiguration;

FIG. 35 is a cross-sectional view of the second bone anchor of FIG. 30in the second configuration;

FIG. 36 is an example of the surgical fixation system according to asixth embodiment of the present invention;

FIG. 37 is an anterior view of the spine with a surgical retractionsystem positioned via a lateral approach to the spine;

FIG. 38 is a perspective view of the base plate of FIG. 1 coupled to anexample of a plate inserter according to one embodiment;

FIG. 39 is a perspective view of the plate inserter of FIG. 38;

FIG. 40 is an exploded view of the plate inserter of FIG. 38;

FIG. 41 is a partial perspective view of the distal insertion head ofthe plate inserter of FIG. 37;

FIG. 42 is a partial perspective view of the distal portion of the plateinserter of FIG. 37;

FIG. 43 is a partial perspective view of the distal portion of the plateinserter with the distal insertion head removed;

FIG. 44 is a cross-sectional view of the plate inserter of FIG. 37coupled to the base plate of FIG. 1 with a pivoting gripping arm of theinsertion and translation assembly in a first configuration;

FIG. 45 is a cross-sectional view of the plate inserter of FIG. 37coupled to the base plate of FIG. 1, with a pivoting gripping arm of theinsertion and translation assembly in a second configuration;

FIG. 46 is a perspective view of the distal end of the plate inserter ofFIG. 37 coupled to the base plate of FIG. 1;

FIG. 47 is a cross-sectional view of the plate inserter of FIG. 37coupled to the base plate of FIG. 1 with a pivoting lever of theinsertion and translation assembly in a first configuration; and

FIG. 48 is a cross-sectional view of the plate inserter of FIG. 37coupled to the base plate of FIG. 1 with a pivoting lever of theinsertion and translation assembly in a second configuration.

DETAILED DESCRIPTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The surgical fixation system and related methodsdisclosed herein boast a variety of inventive features and componentsthat warrant patent protection, both individually and in combination.

FIGS. 1-18 illustrate an example of a surgical fixation system 100according to one embodiment of the present invention. With reference toFIGS. 1 and 2, the surgical fixation system 100 includes a base plate102, a plurality of first bone anchors 104, a plurality of second boneanchors 106, and a translating locking element 108. The example shownherein is in the form of a base plate 102 configured for a single-levelspinal fusion, and as such the base plate 102 is sized and configured tospan a single intervertebral space while achieving purchase within eachof the vertebral bodies adjacent the single intervertebral space. It isto be appreciated, however, the base plate 102 may be provided in anynumber of sizes to accommodate multiple-level spinal fusions withoutdeparting from the scope of the present invention, depending on thespecific needs of the user. The base plate 102 may be provided in anyshape suitable for spanning at least one intervertebral disc spacewithout departing from the scope of the invention. The base plate 102 isparticularly suitable for lateral insertion and placement against alateral aspect of the vertebral bodies, however other uses are possiblewithout departing from the scope of the present invention.

Referring to FIGS. 3-8, the base plate 102 will now be described infurther detail. The base plate 102 has a female component 114 and a malecomponent 116. The female component 114 comprises one first fixationaperture 110, one second fixation aperture 112, a receiving slot 118,and a lengthening slot 120 (FIG. 4). The male component 116 comprisesone first fixation aperture 110, one second fixation aperture 112, aninsertion portion 122, and a locking aperture 124 (FIG. 5). Theinsertion portion 122 of the male component 116 is sized and dimensionedto snugly fit within the receiving slot 118 of the female component 114.The male and female components 114,116 of the base plate 102 aresecuredly mated to one another via translating locking element 108.According to one implementation, a set screw 126 (as shown with a hextooling recess 128) is inserted through the lengthening slot 120 of thefemale component 114 and the locking aperture 134 of the male component116 of the base plate 102, thereby creating a friction fit between themale and female components 114, 116 of the base plate 102.

In its assembled state, the base plate 102 has a first end 130, a secondend 132, a first side 134, and a second side 136. The base plate 102further includes a first surface 138 and an opposing second surface 140.When properly positioned on a lateral aspect of a spinal column, thesecond surf ace 140 interfaces with the bone and thus is a vertebralcontacting surf ace. Moreover, the first end 130 represents thecephalad-most (or top) end of the base plate 102, the first side 134represents the posterior-most (or back) side of the base plate 102, andthe second side 140 represents the anterior-most (or front) side of thebase plate 102. First and second ends 130, 132 preferably each have aradius of curvature that is approximately equal to the radius ofcurvature of the retractor blades 802, 804, 806 (FIG. 37). This issignificant for a number of reasons. Most importantly, having radii ofcurvature of the first and second ends 130, 132 approximately equal theradii of curvature of the retractor blades 802, 804, 806 enables thebase plate 102 to be smoothly advanced along the operative corridortoward the surgical target site. This is a significant advantage whendealing with a minimally-invasive operative corridor in terms ofoperative time savings and avoiding disruption of the operativecorridor.

The base plate 102 is provided with a pair of first fixation apertures110 configured to receive at least a portion of the first bone anchors104 therethrough, and a pair of second fixation apertures 112 configuredto receive at least a portion of the second bone anchors 106therethrough. The first fixation apertures 110 are provided by exampleas large circular holes, however the first fixation apertures 110 may beprovided with any shape suitable for receiving at least a portion of theanchors 104 therethrough, including but not limited to ovoid orpolygonal (e.g. rectangular, triangular, square, etc.) without departingfrom the scope of the present invention. The second fixation apertures112 are provided by example as generally circular apertures, however thesecond fixation apertures 112 may be provided with any shape suitablefor receiving at least a portion of the second fixation apertures 112therethrough, including but not limited to ovoid or polygonal (e.g.rectangular, triangular, square, etc.). As will be explained in furtherdetail below, the fixation apertures 110, 112 are located within thebase plate 102 such that upon proper placement of the base plate 102within a surgical target site, one of the first fixation apertures 110and one of the second fixation apertures 112 are positioned over a firstbone segment (e.g. a first vertebral body), and one of the firstfixation apertures 110 and one of the second fixation apertures 112 arepositioned over a second bone segment (e.g. a second vertebral body).

The first fixation apertures 110 are comprised of a first pocket 142 anda second pocket 144 and are sized and dimensioned to receive the firstbone anchors 104 as will be described in detail below. The secondfixation apertures 112 are shown and described herein as being circularholes. The second fixation apertures 112 have a first pocket 146 and asecond pocket 146 and are sized and dimensioned to receive the secondbone anchors 106 as will be described in detail below.

As depicted in FIG. 7, the second surface 140 of the base plate 102 mayinclude one or more protrusions 150 which engage the bones of thevertebral bodies, the disc space, or the vertebral spacer. Thisengagement prevents the base plate 102 from moving while the pluralityof bone anchors 104, 106 are being placed. Base plate 102 may also haveone or more engagement features 396 for engagement with an insertiondevice, for example translating plate inserter 818 as will be describedin greater detail below. By way of example only, the tool engagementfeatures may be located on the first side 134 (not shown) and secondside 136 of the base plate 102 as shown in FIG. 8.

FIGS. 11-16 illustrate the first bone anchors 104 by way of example onlyin the form of threaded bone screws, however other forms of anchors arepossible without departing from the scope of the present invention. Thebone screw 104 each comprise a screw head 152 and a shank 154. The shank154 includes threads 156 for threaded purchase into a bony segment (e.g.vertebral body).

With reference to FIG. 10-11, the screw head 152 is comprised of anupper screw head region 158, a plurality of locks 160, a lock screw 162,and a bottom spherical portion 164. The upper screw head region 158 isincludes of a plurality of cutouts 166 (which allow for screwdriverengagement as the bone screw 104 is driven into the bone as well astightening the lock screw 162), a plurality of tracks (e.g. T-slottracks 168), an interior chamber 170 (comprising internal threading174), an undercut region 172, and wings 194. As depicted in FIG. 12, theplurality of locks 160 each include an inner lock face 176, an outerlock face 178 having a chamfered bottom surface 180, and a plurality oftabs 182. As FIG. 13 indicates, the lock screw 162 is preferably aconical screw with a proximal end 184, ramped portion 186, a distal end188 with exterior threading 190, and an internal tool engaging recess192. Preferably, the proximal end 184 has a larger diameter than thedistal end 188 of the lock screw 362 which facilitates the use of ascrew driver to retain the lock screw 362.

As shown in FIG. 14, the locks 160 are contained inside the screw head152 under the lock screw 162. The lock screw 162 is contained inside thescrew head 152 under the undercut feature 172 on the interior of thescrew head 170. During assembly, the lock screw 162 is threaded into thebone screw 104 via internal tool engaging recess 192. As the lock screw162 is threaded, the undercut feature 172 splays outward to allow thelock screw 162 to pass. Once the lock screw 162 has passed, the undercutfeature 172 returns to its initial position thereby containing the lockscrew 162 inside the screw head 152. The locks 160 are contained insidethe screw head 152 via tracks 168 which prevent the locks 160 fromrotating, pivoting, or otherwise becoming displaced inside the screwhead 152. The locks 160 are further constrained within the screw head152 by tabs 188 on the locks 160 which abut one or more wings 194 insidethe screw head 152, thereby preventing ejection of the locks 160 out ofthe screw head 152 as depicted in FIG. 16.

The surgical fixation system 100 also includes a locking mechanism forfixedly coupling bone anchors 104 to the base plate 102 afterimplantation. According to one embodiment, fixation apertures 110 eachhave a first spherical pocket 142 and a second spherical pocket 144sized and dimensioned for receiving a bone screw 104 therein. The bonescrew 104 is placed through the base plate 102 and mates with the firstspherical pocket 142 within the base plate 102 via the matching bottomspherical surface 164 of the screw head 152. The bone screw 104 has acone of angulations in which it can be placed and still lock to theplate 102. By way of example only, the cone of angulations may be withina range between O and 10 degrees. Locks 160 have a spherical inner face170 which fit into the second spherical pocket 144. Once the bone screw104 is fully seated with the bottom spherical surface 164 of the screwhead 152 within the first spherical pocket 142, a screw driver mayrotate the lock screw 162 via the inner tool engaging recess 192 towardsthe interior of the screw head 170. As this happens, the ramp 186 of thelock screw 162 slides along the internal lock face 176 to push the lock160 radially outward. When the distal end 188 of the lock screw 162threads into the interior of the screw head 172 via the exteriorthreading 190, the tabs 182 of the lock 160 expand radially outward,causing them to lock the bone screw 104 to the base plate 102 (asdepicted in FIG. 15). With the locks 160 fully engaged in this manner,further polyaxial motion of the bone screw 104 is prevented as isunwanted backout of the bone screw 104. If the lock 160 is in anextended position during screw insertion, the chamfered bottom 180 ofthe outer lock face 178 may guide the lock 160 back into the screw head152 if necessary. It is to be appreciated that in the pockets 142, 144are spherical in this embodiment, they may be any shape includingcylindrical, flat, etc. Furthermore, the outer lock face 178 isspherical in this embodiment, it may be any shape including, but notlimited to, spherical, cylindrical, flat, etc. While the lockingmechanism was explained above with respect to bone screw 104, it is tobe appreciated that the locking mechanism may also be utilized withrespect to a second bone anchor 106.

FIG. 17 illustrates the second bone anchors 106 by way of example onlyin the form of bone staples, however other forms of anchors are possiblewithout departing from the scope of the present invention. The bonestaple 106 comprises a staple head 198 and an elongate body 200. Theelongate body 200 preferably includes a pointed distal tip 202 forpurchase into a bony segment (e.g., vertebral body). Bone staple 106differs from the threaded bone screw 104 in that the bone staple 106does not have threads but rather blades 204 that run down the length ofthe elongate body 200. The flat faces of the blades 204 (shown here byway of example only, in a cruciform configuration) prevent rotation ofthe bone staple 106 about its central axis. Because the bone staple 106is not threaded, it can be impacted into the bone quickly, therebyreducing the time required for implantation. The staple head 198 ismated and locked to the plate 102 via first and second spherical pockets146, 148 the same way as described above for the bone screw 104 and adiscussion of the locking mechanism will not be repeated here.

In minimally invasive lateral approaches to the spine, base plates 102of shorter lengths (defined as the distance between first end 130 andsecond end 132) facilitate the ease of insertion into and through thesurgical corridor. However, depending on patient's anatomy and/orsurgical requirements, base plates 102 of longer lengths may beadvantageous notwithstanding the difficulties associated with insertinga longer plate. In a preferred embodiment of the present invention, thebase plate 102 of the surgical fixation system 100 contains an in situlengthening feature (translating locking element 108) that allows thelength of the base plate 102 to be variably lengthened in situ.Referring back now to FIG. 3, the base plate 102 is shown in itsshortest length configuration (i.e., a closed position). In the closedposition, the male portion 116 of the base plate 102 is fully insertedinto the female portion 114 such that the set screw 126 is maximallysituated within the lengthening slot 120. Referring now to FIG. 6, thebase plate 102 is shown in its longest length configuration (i.e., anopen position). In the open position, the male insertion portion 122 isextended away from the female receiving slot 118 such that at least someportion of the male insertion portion 122 is not contained within thefemale receiving slot 118. This distance of such a non-contained portionis limited by the distance between the two ends of the lengthening slot120 within the translating locking element 108. This distance can be anyanatomically-appropriate distance, for example, somewhere within a rangebetween 0.1 mm and 5 mm, for example 2 mm. In the open position, the setscrew 126 is minimally situated within the lengthening slot 120.

In a preferred embodiment, the base plate 102 is inserted in itssmallest, closed configuration via a lateral approach to lateral aspectof the spine. Once the base plate 102 has reached the spinal targetsite, the plate 102 may be lengthened until the set screw 126 preventsany further extension within the lengthening slot 120. However, it is tobe appreciated that the base plate 102 may be lengthened any distanceallowed by the translating locking element 1308 based upon patientanatomy and surgical requirements. Once the desired length has beenachieved, the translating locking element 108 may be secured, therebylocking the length into position. To do this, the set screw 126 may bedriven down, via tooling recess 128 as shown in FIG. 18. As the setscrew 126 is driven down, the threads (not shown) on the lockingaperture 124 of the male component 116 push against one another. Oncethe set screw 126 is fully advanced, it drives the top of the malecomponent 116 upwards towards the top of the female component 114,thereby locking the base plate 102 into the desired length.Additionally, the engagement surfaces on the male component 116 andfemale component 114 may be textured to increase the friction betweenthe two when the base plate 102 is locked into its final configuration.The base plate 102, anchors 104, 106, and/or locking components 160,162, etc. may be formed of any material suitable to provide rigidfixation between two bony segments. By way of example, all may be formedof a biocompatible metal, such as titanium. The base plate 102 may beprovided with any size necessary to complete the desired spinalfixation.

FIGS. 19-20 illustrate a second embodiment of the surgical fixationsystem 300. The surgical fixation system 300 is similar to surgicalfixation system 100 except that it has threaded bone staples 302 insteadof unthreaded bone staples. Threaded bone staple 302 (FIG. 20) comprisesa staple head 304 and an elongate body 306. The elongate body 306includes threads 308 for threaded purchase into a bony segment (e.g.vertebral body). The threaded bone staple 306 is mated and locked to theplate the same way as described above for the bone screw 104. It is tobe appreciated that surgical fixation system 300 includes all othercomponents and features of surgical fixation system 100 such that adiscussion of those components and features will not be repeated here.

FIG. 21 illustrates a third embodiment of the surgical fixation system400. The surgical fixation system 400 is similar to surgical fixationsystem 100 except that it has a pair of first fixation apertures 110 forreceiving a pair of first bone anchors 104 and a singular fixationaperture 112 for receiving one bone anchor 106 (e.g. bone staple 106).It is to be appreciated that surgical fixation system 400 includes allother components and features of surgical fixation system 100 such thata discussion of those components and features will not be repeated here.FIG. 22 illustrates a fourth embodiment of the surgical fixation system500. The surgical fixation system 500 is similar to surgical fixationsystem 100 except that it does not include second fixation apertures 112and thus does not receive bone anchors 106. It is to be appreciated thatsurgical fixation system 500 includes all other components and featuresof surgical fixation system 100 such that a discussion of thosecomponents and features will not be repeated here. FIGS. 23-35illustrate a fifth embodiment of the surgical fixation system 600. Withreference to FIGS. 23 and 24, the surgical fixation system 600 includesa base plate 602, a plurality of first bone anchors 604, a plurality ofsecond bone anchors 606, and a translating locking element 608. Theexample shown herein is in the form of a base plate 602 configured for asingle-level spinal fusion, and as such the base plate 602 is sized andconfigured to span a single intervertebral space while achievingpurchase within each of the vertebral bodies adjacent the singleintervertebral space. It is to be appreciated, however, the base plate602 may be provided in any number of sizes to accommodate multiple-levelspinal fusions without departing from the scope of the presentinvention, depending on the specific needs of the user. The base plate602 may be provided in any shape suitable for spanning at least oneintervertebral disc space without departing from the scope of theinvention. The base plate 602 is particularly suitable for lateralinsertion and placement against a lateral aspect of the vertebralbodies, however other uses are possible without departing from the scopeof the present invention. It is to be appreciated that the base plate602 includes all components and features of the base plate 102 such thata discussion of those components and features will not be repeated here.

The first bone anchors 604 are shown and described herein by way ofexample only (FIGS. 25-29), in the form of threaded bone screws, howeverother forms of anchors are possible without departing from the scope ofthe present invention. The bone screws 604 each comprise a head region648 and a shank 650. The shank 650 includes threads 652 for threadedpurchase into a bony segment (e.g. vertebral body).

The head region 648 is comprised of a screw head 654, a screw cap 656, awasher 658 (preferably a split-ring washer), and a bottom sphericalsurface 660. The screw head 654 is further comprised of an inner toolengaging recess 662 for engaging with a tool capable of driving thescrew into bone (e.g. a hex recess as shown in FIG. 25) and an exteriorthread 664. The cap 656 is further comprised of an open proximal end666, an outer tooling recess 668 capable of driving the screw cap 656 intowards the spherical bottom surface 660 of the head 654, a tapereddistal end 670, and internal threading 672 disposed within the inneraperture 674 (which preferably extends from just below the outer toolingrecess 668 all the way to the tapered distal end 670).

The cap 656 is sized and dimensioned to be positioned through the splitring washer 658 and at least partially threadably advanced within theexternal threading 664 on the screw head 654. Between the top of the cap656 and the washer 658, there is a circumferential recess 676. Withinthis recess, the washer 658 is freely able to spin around the screw head654 and move between the top and bottom surfaces of the screw head 654.

The bone screw 604 is placed through the base plate 602 and mates with afirst spherical pocket 642 within the base plate 602. The bone screw 604has a cone of angulations in which it can be placed and still lock tothe plate 602. By way of example only, the cone of angulations may bewithin a range between O and 10 degrees. Once the bone screw 604 isfully seated with the bottom spherical surface 660 of the screw head 654within a first spherical pocket, a driver mechanism may rotate the screwcap 656 via the outer tooling recess 668 such that the screw cap 664 isadvanced towards the bottom spherical surface of the screw head 654. Asthis happens, the screw cap 656 compresses the split ring washer 658 andforces the washer 658 radially outward into a second spherical pocket644 in the base plate 602. The force of the split ring washer 658 on thebase plate 602 prevents the first bone anchor 604 from rotating orbacking out. With the bone screw 604 fully positioned within the firstfixation aperture 610, the bone screw 604 is prevented from rotatingabout its axis, rotating about its head 654, and translating within theaperture 610.

The second bone anchors 606 are shown and described herein by way ofexample only, in the form of a bone staple in FIGS. 30-35, however otherforms of anchors are possible without departing from the scope of thepresent invention. A bone staple 606 may provide the advantages of beingsmaller, faster to insert, and the ability to resist rotation ascompared to threaded bone screws (e.g., threaded bone screws 604). Asdepicted in FIGS. 30-31, the bone staples 606 each comprise a headregion 678 and an elongated shaft 680. The elongated shaft 680 comprisesa plurality of orthogonally-disposed fins 682 and a pointed distal tip684 designed for purchase within a bony segment (e.g. a vertebral body).

The head region 678 is comprised of an upper head portion 686 with aplurality of cutouts 688, a plurality of independent tabs 690 extendingthrough the cutouts 688, and a bottom spherical surface 692 (FIGS.32-33). The upper head portion 686 is further comprised of an inner toolengaging recess 694 disposed on the top of the head 678, which may be ahex recess as shown in FIG. 30. The bone staple 606 is placed throughthe base plate 602 and mates with a spherical pocket within the baseplate 602. The bone staple 606 has a cone of angulations in which it canbe placed and still lock to the plate 602. By way of example only, thecone of angulations may be within a range between O and 10 degrees. Oncethe bone screw 606 is fully seated with the bottom spherical surface 692of the upper head portion 686 within the spherical pocket, a drivermechanism forces a conical screw 696 disposed within the head region 678down into the bone staple 606. As this happens, the conical screw 696deforms the tabs 690 radially outward towards the base plate 602 (FIGS.34-35). The force of the tabs 690 on the base plate 602 prevents thebone staple 606 from rotating or backing out.

In minimally invasive lateral approaches to the spine, base plates 602of shorter lengths (defined as the distance between first end 630 andsecond end 632) facilitate the ease of insertion into and through thesurgical corridor. However, depending on patient's anatomy and/orsurgical requirements, base plates 602 of longer lengths may beadvantageous notwithstanding the difficulties associated with insertinga longer plate. In a preferred embodiment of the present invention, thebase plate 602 of the surgical fixation system 600 contains an in situlengthening feature that may be the same as discussed above withrelation to the translating locking element 108. As such, this featurewill not be repeated here.

FIG. 32 illustrates a sixth embodiment of the surgical fixation system700. The surgical fixation system 700 is similar to surgical fixationsystem 600 except that it does not include second fixation apertures 612and thus does not receive bone anchors 606. It is to be appreciated thatsurgical fixation system 700 includes all other components and featuresof surgical fixation system 600 such that a discussion of thosecomponents and features will not be repeated here. Although shown anddescribed above as assembled in space, the surgical fixation systems ofthe present invention are assembled in situ during a surgical procedure.One such example is a spinal fusion surgery. The surgical fixationsystems disclosed herein are optimally used in a direct lateral surgicalprocedure in which the spine is approached laterally at approximately a90° angle relative to the patient's spine. The first step in such aprocedure is to create an operative corridor through the patient's skinand underlying musculature to the spinal target site, for example, asymptomatic intervertebral disc located between first and secondadjacent vertebral bodies. The specific technique involved in performingthis step is shown and described in commonly-owned U.S. Pat. No.7,905,840, filed on Oct. 18, 2004, patented on Mar. 15, 2011, andentitled “Surgical Access System and Related Methods,” the entirecontents of which are hereby incorporated by reference into thisdisclosure as if set forth fully herein.

A key component of the technique of establishing the operative corridoris the surgical retraction system 800 (FIG. 37). Notably, the surgicalretraction system 800 includes a plurality of retractor blades 802, 804,806. The surgical retraction system 800 is introduced into the surgicaltarget site in an initial “closed” position wherein the retractor blades802, 804, 806 together form a generally cylindrical tubular member.Thereafter, the surgical retraction system 800 is moved to an “open”position in which the retractor 802, 804, 806 are spread apart from oneanother, thereby establishing the operative corridor to the surgicaltarget site. As the three blades 802, 804, 806 initially form agenerally cylindrical tubular member in a closed position, each bladehas a defined radius of curvature. This radius of curvature isapproximately equal to the radius of curvature of the first and secondends 130, 132 of the base plate 102 as discussed above.

After establishment of the operative corridor to the surgical targetsite, the next step is to perform the necessary therapeutic technique torelieve the distress on the target disc space. For example, this mayinvolve performing a partial or total discectomy (removing damaged ordegenerative disc tissue from the intervertebral space) and theninserting a spinal fusion implant such as a bone graft (e.g., allograft,autograft, or xenograft) or synthetic fusion cage (e.g., titanium and/orPEEK) into the space. One example of a synthetic spinal fusion implantthat may be used is shown and described in commonly-owned U.S. Pat. No.7,819,891 filed on Mar. 29, 2005, issued on Apr. 5, 2011, and entitled“Systems and Methods for Spinal Fusion,” the entire contents of whichare hereby incorporated by reference into this disclosure as if setforth fully herein. These spinal fusion implants (natural or synthetic)may be used with or without additional fusion-inducing materials, suchas an orthopedic matrix containing, for example, calcium hydroxyapatite,bone morphogenic protein (BMP), demineralized bone matrix, collagen bonegraft matrix, and stem cell material, or other fusion-promotingsubstances placed within the spaces of the implant, while the implant isadvanced into the intervertebral space.

Referring to FIG. 37, a surgical target site 808 is shown comprising afirst vertebral body 810, a second vertebral body 812, and anintervertebral disc space 814 situated between the first and secondvertebral bodies 810, 812. A spinal fusion implant 816 has been insertedinto the disc space 814. With the distressed disc space addressed, thenext step is to add supplemental fixation, if desired.

In this case, the surgical fixation system 100 of the present inventionis implanted through the operative corridor within the surgical targetsite 808 to help with the fusion process. While the steps of implantingthe surgical fixation system is described herein with respect tosurgical fixation system 100, it is to be appreciated that surgicalfixation systems 300, 400, 500, 600, and 700 may also be implanted in asimilar manner.

The first step in implanting the surgical fixation system 100 is toimplant an appropriately-sized bone plate 102 over the first and secondvertebral bodies 810, 812. According to one implementation, the size ofthe base plate 102 relates to its size in the open position andcorresponds to the size of the spinal fusion implant 816. This allowsfor insertion of the base plate 102 in its closed position through thesurgical retraction system 800 and expansion into its open position (viatranslating locking mechanism 108) at the surgical target site 808. Asdescribed in FIGS. 38-48, there is also provided a plate inserter 818for inserting the surgical fixation system 100, preferably from alateral approach. The plate inserter 818 is comprised of a handle 820,an elongate tubular element 822, and an insertion and translationassembly 824, as illustrated in FIGS. 38-39.

The handle 820 is generally disposed near the proximal end of the plateinserter 818. The handle may be further equipped with a universalconnector feature 826 to allow for ease of attachment with the elongatetubular element 822 via handle adapter 828.

The elongate tubular element 822 includes a handle adapter 828, an innerbore 830, and a distal insertion head 832. The handle adapter 828 isremoveably coupled to the handle 820 via the universal connector feature826. The inner bore 830 extends from the proximal to the distal ends ofthe elongate tubular element 820 and is dimensioned to receive the outershaft 844 and the inner shaft 846 of the insertion and translationassembly 824. As best viewed in FIG. 41, the distal insertion head 832is comprised of a central opening 834, a fixed gripping arm 836 with aplate engagement feature 838, a lateral slot 840, and a plurality ofpin-receiving apertures 842 for receiving one or more pivot pins 858.The central opening 834 of the distal insertion head 832 extendsdistally from the inner bore 830 of the elongate tubular element 822.The central opening 834 houses one or more components of the insertionand translation assembly 824 including the outer shaft 844, the innershaft 846, the pivoting gripping arm 850, and the pivoting lever 852which is shown in FIG. 42 and as will be described in greater detailbelow.

The elongate tubular element 822 is dimensioned to receive a spring (notshown) and one or more actuating knobs 854, 856 comprising part of theinsertion and translation assembly 826 at its proximal end. The elongatetubular element 822 is generally cylindrical and of sufficient length toallow the plate inserter 818 to span from the surgical target site to alocation sufficiently outside of the patient's body so the handle 820and actuating knobs 854, 856 can be easily accessed by the surgeon or acomplimentary controlling device.

The insertion and translation assembly 824 is comprised of outer shaft844, an inner shaft 846 disposed within the central lumen 848 of theouter shaft, a pivoting gripping arm 850 having at least one pivotinglinkage and a plate engagement feature 838, a pivoting lever 852, afirst actuating knob 854 for actuating the pivoting gripping arm 850,and a second actuating knob 856 for actuating the pivoting lever 852. Atleast a portion of the insertion and translation assembly 824 extendinto the central opening 834 of the distal insertion head 832.

The pivoting gripping arm 850 is housed within the distal insertion head832 at least partially through the lateral slot 840. The lateral slot840 is sized and dimensioned such that a lateral aspect of the pivotinggripping arm 850 is seated within the lateral slot 840. The pivotinggripping arm 850 includes a pivot pin 858 which is received within thepin-receiving apertures 842 on the distal insertion head 832 whichprovides a fixed point for the pivoting gripping arm 850 to rotate inrelation to the distal insertion head 832 as the base plate 102 issecurely tightened to the plate inserter 818.

The pivoting lever 852 is centrally housed at least partially within thedistal insertion head 832 and includes a curved proximal region 860situated adjacent the distal end of the inner shaft 846, a tapereddistal region 862 for engaging with the hex recess 128 in the set screw126 of the base plate 102, and a spring-loaded pivot mechanism 864.

FIG. 43 depicts the distal portion of the insertion and translationassembly 824 including the distal aspects of the outer and inner shafts844, 846, pivoting gripping arm 850 and the pivoting lever 852 with thedistal insertion head 832 removed for illustrative purposes. Referringto FIGS. 44-46, the step of inserting the base plate 102 into operativecorridor will now be described in detail. The pivoting gripping arm 850is biased in a closed position via a spring loaded mechanism (not shown)but will hinge to the open position with the application of downwardpressure. The plate inserter 818 may engage the base plate 102 byplacing the plate engagement features 838 of the fixed and pivotinggripping arms 836, 850 adjacent to the engagement features 198 of thebase plate 102. The application of downward pressure will force thepivoting gripping arm 150 into an open position such that it may bereceived into its engagement feature 198. Rotating the first actuatingknob 854 clockwise tightens the plate inserter 818 to the base plate102. With the base plate 102 securely attached to the plate inserter818, the base plate 102 may then be inserted through the retractorblades 802, 804, 806 and centered over the spinal fusion implant 816 oneither side of the vertebral bodies 810, 812. The position of the baseplate 102 may then be checked using lateral fluoroscopic imaging.

Referring now to FIGS. 47-48, the step of lengthening the base plate 102in situ will now be described in detail. The pivoting lever 150 isbiased in a first position by a spring loaded mechanism 864 to keep thebase plate 102 in the closed configuration described above. Turning thesecond actuating knob 856 in the clockwise direction advances the innershaft 846 towards the curved proximal region 860 of the pivoting lever150. As the inner shaft 846 is advanced it slides along the top of thecurved proximal region and causes it to be displaced and pivot, which inturn causes the tapered distal region 862 to translate within the hexscrew recess 128 of the set screw 128 thereby lengthening the base plate102. With the second actuating knob maximally advanced, the pivotinglever 852 is located in a second position forcing the plate into theopen configuration described above. Turning the second actuating knob856 in the counter-clockwise direction retracts the inner shaft 846which causes the pivoting lever 852 to return to its biased, firstposition. A/P fluoroscopic imaging may be used to verify that the baseplate 102 is properly centered on the vertebral body and the elongatetubular member 122 is aligned with the disc space 814.

Once the base plate 102 is properly seated within the surgical targetsite 808, the surgeon proceeds with pilot hole formation to prepare thevertebral bodies 810, 812 for receiving the first bone anchors 104. Itis to be appreciated that the plate inserter 818 is still engaged to thebase plate 102 during pilot hole formation to ensure that the base plate102 does not move from its optimal position. Formation of the pilot holemay be accomplished via a number of different techniques and instrumentsdepending upon the surgeon's preference, including but not limited tousing drills, taps, awls, etc. to create a pilot hole that is preferablyundersized by 1 mm relative to the first bone anchors 104 to be used inorder to maximize the purchase of the bone screws 104 within the bone.By way of example only, a self-centering adjustable awl and/or aself-centering adjustable drill may be used to prepare each pilot hole.Fluoroscopic imaging and depth stops on the awl and drill may beutilized during pilot hole formation to ensure proper depth of the pilothole.

Upon formation of the pilot hole, the bone screws 104 are inserted intothe bone. It is to be appreciated that the plate inserter 818 is stillengaged to the base plate 102 during the insertion of the bone screws104 to ensure that the base plate 102 does not move from its optimalposition. Insertion of the bone screws 104 may be accomplished via anumber of different techniques and instruments depending on thesurgeon's preference. Preferably, a screwdriver (not shown) with teeththat complementary to the cutouts 166 of the screw head 152 is used tosolidly engage the cutouts 166 of the bone screw 104 for insertion intothe bone. The bone screw 104 is then advanced through the pilot holeusing A/P fluoroscopy for guidance until the screw head 152 is slightlyproud above the base plate 102. The screwdriver may then be removed fromthe bone screw 104. Pilot hole preparation and bone screw insertion isrepeated for the remaining bone screw 104.

After the bone screws 104 are placed, the bone staples 106 may then beplaced within the first and second vertebral bodies 810, 812. Bonestaples 106 do not require pilot hole preparation and their insertionmay be accomplished via number of different techniques and instrumentsdepending on the surgeon's preference. Preferably, a driver capable ofdelivering a staple (not shown) with teeth complementary to the cutoutson the staple head 204 is used to solidly engage the cutouts of the bonestaple 106 for insertion into the bone. According to one embodiment, theintended trajectory of the bone staples 106 is 5° in theanterior-posterior direction and 5° divergent from the endplates of thevertebral body 810 or 812. Using A/P fluoroscopy for depth guidance, thebone staple 106 is then impacted until the staple head 204 is capturedwithin the first spherical pocket 146 of the base plate 102. Stapleinsertion is repeated for the remaining bone staple 106.

With the bone screws 104 and bone staples 106 positioned, the next stepis final tightening of the construct. Tightening of the construct may beaccomplished via a number of different techniques and instrumentsdepending upon the surgeon's preference. By way of example, a torqueT-handle (preferably with a torque-limiting setting of e.g., 45 in./lb.,not shown), may be attached to a driver instrument (not shown) andplaced through the distal end of a counter-torque instrument (notshown). The distal hex of the driver instrument may be seated into thelock screw 162 of the bone screw 104. Final tightening may be performedby holding the counter-torque device while rotating the torque T-handleuntil an audible click is heard. The bone screw 104 will be secured tothe base plate 102 via the locking mechanism as described above. Thisstep may be repeated for the remaining bone screw 104 and bone staples106. If the surgical bed was broken (angled near the middle) tofacilitate access to the disc space during the procedure, it may then bereturned to a flat position to ensure maximum axial load (compression)is placed on the spinal fusion implant 816 to facilitate fusion. By wayof example, the base plate 102 may allow for 2 mm of compression.

Next, the translating locking element 108 may be tightened. By way ofexample, the translating mechanism may be tightened via thetorque/counter-torque method described above by engaging the hex recess128 of the set screw 126 on the translating locking element 108, holdingthe plate counter-torque while rotating the torque T-handle clockwiseuntil an audible click is heard. At this point, the construct is fullyassembled and locked in place. The surgical retraction system 800,including retractor blades 802, 804, 806 may be closed and removed fromthe patient. This effectively closes the operative corridor. Theprocedure being completed, the incision may be stitched up.

While this invention has been described in terms of a best mode forachieving this invention's objectives, it is understood by those skilledin the art that variations may be accomplished in view of theseteachings without deviating from the spirit or scope of the invention.

We claim:
 1. A system for fixing a first bone segment to a second bonesegment, comprising: a base plate assembly having a first component anda second component, the first component configured to receive at least aportion of the second component therethrough, and an expandable lockingmechanism to fixedly engage the first and second components in at leasta first, closed configuration and a second, open configuration; whereinthe base plate assembly has a first end, a second end, first and secondsides extending between the first and second ends, and first and secondsurf aces extending between the first end, second end, first side, andsecond side, the first and second surf aces separated by a thickness ofthe base plate, the base plate including a first pair of fixationapertures and a second pair of fixation aperture extending through thebase plate between the first and second surfaces and dimensioned toreceive at least a portion of a fixation element extending therethrough;a plurality of first fixation elements; and a plurality of secondfixation elements.